Auditory Processing are the neurological events after the perception of sound that allow an individual to make sense of what he/she hears. Auditory Processing Disorders (APD) are disabilities whose prevalence and societal burden are unknown. The inability to accurately process auditory signals provides a challenge to learning and language acquisition, especially in crowded or noisy classrooms. There is abundant evidence in the scientific literature that in many cases APD coexists with, and may be the underlying cause of, a learning and/or language disability such as dyslexia, autism or specific language impairment (SLI). However, the association of APD and these heterogeneous language disorders is controversial. And although clinicians have testing procedures that allow for the identification of frank disabilities in auditory processing, the variation in processing skills among normal individuals is not well-known. We are assessing the normal variation using a variety of tests of auditory processing. We are evaluating these skills in twin pairs. By comparison of the performance between identical and fraternal twin pairs we can also estimate the contribution that genes and environment make to these traits.